Networked Control Systems Subject Research Articles

Observed-Mode-Dependent Nonfragile Control of Networked Control Systems Under Hidden DoS Attacks

This paper develops a methodology on observed-mode-dependent non-fragile control for networked control systems subject to denial-of-service attacks, which takes the strong concealment of attack behavior into account. To describe complex switching phenomenon between different forms of attacks that the adversary may launch on communication channels, the semi-Markov chain is introduced. DoS attacks with stealth characteristic is analyzed from hidden semi-Markov jump systems perspective by constructing a double-layer stochastic process consisting of semi-Markov chain and observed mode sequence. With the aid of emission probability, an observed-mode-dependent non-fragile controller is designed, which can still stabilize the system even if actual attack modes are unavailable. By utilizing the Lyapunov function that depends on actual attack modes and observed ones, sufficient conditions to ensure the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\delta$</tex-math></inline-formula> -error mean square stability of the closed-loop system is deduced. Eventually, a simulation related to the mass-spring-damper system with single channel and an example of the unmanned ground vehicle with two channels are studied, both of which demonstrate the feasibility and validity.

Dynamic Periodic Event-Triggered Control for Networked Control Systems Under Packet Dropouts

This article presents a co-design method of dynamic periodic event-triggering mechanism (DPETM) and output-based control law for networked control systems (NCSs) subject to inevitable imperfections such as limited network resources, exogenous disturbances and successive packet dropouts. The developed DPETM has the potential to make full use of scarce network resources compared to the periodic sampled-data control on the one hand, and is natural for practical digital platforms instead of a discretized version of continuous event-triggered control (CETC) one the other hand. In this paper, the whole closed-loop system is modeled a unified hybrid system by incorporating bilateral DPETM, successive packet dropouts effects and external disturbances, and an improved hybrid Lyapunov function is constructed for stability analysis. Based on the hybrid framework, some sufficient conditions are presented to guarantee <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal{L}_2$</tex-math> </inline-formula> -stability of the system while tolerating a maximum allowable number of successive packet dropouts (MANSD). Furthermore, new linear matrix inequality (LMI) conditions for co-design of control law and triggering strategy are derived by introducing some constraints with the free variables and a modified Young’s inequality. In addition, this paper considers two scenarios relating to whether an acknowledgment scheme is employed or not. Finally, the effectiveness of the proposed method is verified by two illustrated examples and comparative studies. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —With the increasing requirement for reducing unnecessary waste of communication resources in modern industries, it is necessary to consider an alternative paradigm of the time-triggered control. In many digital control applications such as smart power grid, vehicle and remote surgery, the control tasks are often executed periodically, which makes it difficult for the theoretical results of CETC to be directly applied to practical digital platforms. The DPETM proposed in this paper, which only verifies the triggering conditions periodically at each sampling instant, is more suitable for practical digital platforms such as time-sliced embedded architectures compared to CETC. This paper investigates the stability problem for NCSs with DPETM subject to packet dropouts. Different from most of the existing literature on randomness of packet loss, this paper focuses on impact of the continuity of packet dropouts on system performance. Based on the hybrid framework and the Lyapunov approach, a co-design methodology of triggering condition and control law is proposed to ensure that the system satisfies the desired performance and can admit a MANSD.

Stability Guarantees for a Class of Networked Control Systems Subject to Stochastic Delays

Stability Guarantees for a Class of Networked Control Systems Subject to Stochastic Delays

Necessary and sufficient optimal control conditions for networked control systems with input delay and Markovian packet dropouts

AbstractThis article studies the optimal control for networked control systems (NCSs) subject to Markovian packet dropouts and input delay. In this scenario, Markovian packet dropouts occur in two channels, that is, from sensor to controller and from controller to actuator. Meanwhile, the input delay arises in the channel from controller to actuator. The contributions of this paper are as the following two aspects: Firstly, based on Pontryagin's maximum principle, the solution to the forward and backward stochastic difference equations (FBSDEs) is obtained. Secondly, in virtue of the obtained solution to the FBSDEs, sufficient and necessary optimal control conditions are derived and the explicit expression of the optimal controller is presented. The validity of the results is illustrated by numerical examples.

Event-triggered [formula omitted] stabilization of networked cascade control systems under periodic DoS attack: A switching approach

This paper deals with the H∞ control design for the networked cascade control systems (NCCSs) subject to periodic denial-of-service (DoS) attack. The controller structure is based on the state-feedback controller for the both control loops. The communication network of the primary loop is equipped with an event-triggered mechanism while the network is under periodic DoS attack. For stability analysis and controller design, the mathematical model of the closed-loop system is formulated based on the switching systems approach. By using the piecewise Lyapunov-functional-based approach and average dwell time techniques, some stability and stabilization criteria are derived and presented in the form of linear matrix inequalities (LMIs). Finally, an steam temperature cascade control system is utilized as a practical example to demonstrate the effectiveness of the proposed method.

Event-triggered [formula omitted]-gain control for networked systems with time-varying delays and round-robin communication protocol

This paper studies the event-triggered (ET) L2-gain control issues for time-delay networked control systems (NCSs) subject to round-robin protocol. The considered NCS consists of n sensor nodes, where the communication from the sensors to the controller is scheduled by round-robin protocol. This protocol requires that, at every sampling instant, only one sensor is chosen to use the sensor/controller network and transmits its measurement information toward the controller. On the other hand, the ET strategy is adopted in the controller/actuator network, which means that the actuator will receive the updated control input signal in the situation that the predefined ET conditions are satisfied. The utilization of round-robin protocol and ET strategy will help to relieve the burden of network transmission. The network resources and bandwidth will be saved. By developing appropriate Lyapunov functional, sufficient conditions in matrix inequalities are established in order to achieve the stability and L2-gain of the studied systems. Then, a novel iterative algorithm is presented to solve the derived stability conditions so as to design the controllers and obtain the minimal L2-gain simultaneously. Two examples are executed at last to demonstrate the validness and benefits of our results.

An Adaptive Filter-Based Equivalent-Input-Disturbance Approach for Networked Control Systems With Measurement Noise

This paper addresses the disturbance rejection problem for networked control systems (NCSs) subject to time-varying delays and measurement noise. Firstly, the uncertainty caused by the delay is modeled to be a delay-induced disturbance (DID) and treated as part of the lumped disturbance. Secondly, an adaptive-filter-based EID (AFEID) estimator is proposed to estimate this lumped disturbance under the effect of measurement noise. A new filter is designed by introducing an adjustable zero. Then, an adaptive characteristic-adjustment mechanism is constructed for the filter to resolve the contradiction between fast disturbance reconstruction and measurement noise attenuation. Finally, experimental results reveal the superiority of the proposed method.

Hybrid Dynamic Event-Triggered Control for Networked Control Systems Subject to Asynchronous DoS Attacks

Hybrid Dynamic Event-Triggered Control for Networked Control Systems Subject to Asynchronous DoS Attacks

Suppression of Packet Losses and Disturbances in Networked Control Systems Based on Equivalent-Input-Disturbance Approach.

This article presents a method of suppressing packet losses and exogenous disturbances for a networked control system (NCS) subject to network-introduced delays. The NCS has two feedback loops: 1) a local one and 2) a main one. The local feedback loop contains a state observer, an equivalent-input-disturbance (EID) estimator, and state feedback. It is used to ensure prompt disturbance suppression. The controller in the main feedback loop contains an internal model to track a reference input. The system is divided into two subsystems for the design of controllers. The state-observer gain is designed for one subsystem using the concept of perfect regulation to ensure disturbance estimation performance. The state-feedback gains of the other subsystem are designed based on a stability condition in the form of a linear matrix inequality (LMI). A tracking specification is embedded in the LMI-based stability condition to ensure satisfactory tracking performance. A case study on a two-finger robot hand control system and a comparison with a Smith-EID and H∞ controller approach validate the effectiveness and superiority of the presented method.

Observer-based model predictive control for uncertain NCS subject to hybrid attacks via interval type-2 T–S fuzzy model

In this study, an observer-based model predictive control (MPC) algorithm is addressed for an uncertain discrete-time nonlinear networked control system (NCS) subject to hybrid malicious attacks by using interval type-2 Takagi–Sugeno (IT2 T–S) fuzzy theory. Hybrid malicious attacks, including two typical attacks, i.e., denial-of-service (DoS) attacks and false data injection (FDI) attacks, are considered in the communication networks. Under DoS attacks, the control signals will be interfered, which cause the degradation of signal-to-interference-plus-noise ratio, then lead to packets loss. Under FDI attacks, the false signals are injected and output signals are modified so that the system performance is deteriorated. For the NCS subject to hybrid attacks, a secure observer that can resist FDI attacks is devised and a fuzzy MPC algorithm that can solve the controller gains is proposed. Besides, by updating the bound of augmented estimation error, the recursive feasibility can be guaranteed. Finally, illustrative examples are given to show the effectiveness of proposed scheme.

Optimal Control and Stabilization for Networked Control Systems Subject to Intermittent Observations and One-step Delayed Measurement

Optimal Control and Stabilization for Networked Control Systems Subject to Intermittent Observations and One-step Delayed Measurement

Stabilization of Networked Control Systems Subject to Consecutive Packet Dropouts: The Random Clock Offsets Case

In this article, the stabilization problem is investigated for a class of networked control systems with random clock offsets and consecutive packet dropouts. Different from the existing literature, the consecutive packet dropouts occurring in communication networks are subject to clock offsets, and the clock offsets between the sensor and the controller are described by a random variable with a certain probability distribution. First, we construct a closed-loop discrete-time stochastic system by considering the random clock offsets and the consecutive packet dropouts in a unified framework. To render the discrete-time system suitable for analysis, an equivalent yet tractable stochastic augmented model is then established, where the system matrix is characterized by high nonlinearity and dual randomness, which poses substantial difficulties for the expectation operation in the controller design process. In order to deal with the difficulties, the law of total expectation, confluent Vandermonde matrix, and Kronecker product operation are introduced and then a stability condition in the form of linear matrix inequality is obtained. Based on this, a desired controller is designed, such that the closed-loop stochastic system is stochastically stable. Finally, a numerical example with two cases and an example using batch reactor are provided to demonstrate the effectiveness of the proposed design approach.

Periodic Event-Triggered Networked Control Systems Subject to Large Transmission Delays

This article studies periodic event-triggered networked control for nonlinear systems, where the plants and controllers are connected by multiple independent communication channels. Several network-induced imperfections are considered simultaneously, including time-varying intersampling times, sensor node scheduling, and especially, large time-varying transmission delays, where the transmitted signal may arrive at the destination node after the next transmission occurs. A new hybrid system approach is provided to model the closed-loop system that contains all communication related behavior. Then, by constructing new storage functions on the system state and updating errors, the relationship between the maximum allowable sampling period and maximum allowable delay number in sampling is analyzed, where the latter denotes how many inter-sampling periods can be included in one transmission delay. Moreover, to efficiently reduce unnecessary transmissions, a new dynamic event-triggered control scheme is proposed, where the event-triggering conditions are detected only at aperiodic and asynchronous sampling instants. From emulation-based method, where the controllers are initially designed by ignoring all the network-induced imperfections, sufficient conditions on the dynamic event-triggered control are given to ensure closed-loop input-to-state stability with respect to external disturbances. Finally, two nonlinear examples are simulated to illustrate the feasibility and efficiency of the theoretical results.

Dual‐terminal event‐triggered dynamic output feedback H∞ control for aero engine networked control systems with quantization

AbstractThis study deals with the problem of dual‐terminal event‐triggered dynamic output feedback (DOF) control for aero engine networked control systems (NCSs) subject to network‐induced delay, external disturbance, and quantization effects. First, we established a generalized mathematical model of the aero engine. Second, a dual‐terminal dynamic event‐triggered mechanism (DETM) was designed to reduce the utilization of the network bandwidth. In addition, a DOF controller with a compensation function was proposed to stabilize the system. By utilizing the Lyapunov‐Krasovskii (LK) method, the stability criteria were determined. Accordingly, the design conditions of the DOF controller and DETMs were presented. Furthermore, based on a genetic algorithm (GA), a parameter tuning method was proposed to obtain the allowable delay upper bound with less conservatism. Finally, some examples were presented to show the effectiveness and superiority of the presented scheme.

Stabilization of Networked Control Systems Subject to Noisy Sampling Intervals and Stochastic Time-Varying Delays

In practical engineering, the sampling intervals of networked control systems are often subject to undesirable physical constraints, which results in noisy sampling intervals. In view of this, we focus on the linear plants without unknown parameters and investigate the stabilization problem of networked control systems with noisy sampling intervals and stochastic time-varying delays. First, a closed-loop discrete-time stochastic system, whose system matrices are characterized by high nonlinearity and randomness, is obtained by considering the noisy sampling intervals and stochastic time-varying delays in a unified framework. Second, an equivalent yet tractable stochastic-augmented model is established with the aid of matrix exponential computation. With a confluent Vandermonde matrix associated with the minimal polynomial and Kronecker product operation, the mathematical expectation of a product of three matrices, including the system matrix of the stochastic-augmented model and its transpose, is calculated. Based on this, a stabilization controller is designed such that the stochastic stability of the original discrete-time stochastic system is guaranteed. Finally, an illustrative example with four different cases is provided to verify the effectiveness of the designed method.

Event-Triggered Cognitive Control for Networked Control Systems Subject to DoS Attacks and Time Delay

Event-Triggered Cognitive Control for Networked Control Systems Subject to DoS Attacks and Time Delay

Dynamic event-triggered H∞ filtering for discrete-time singular networked control system subject to cyberattacks

This paper investigates the event-triggered filtering problem for the discrete-time singular networked control systems (DSNCS) with random cyberattacks. To more effectively utilize the limited network resource, a new dynamic event-triggered mechanism is proposed, which can effectively reduce network information transmission and save bandwidth on the premise of ensuring system performance. By considering the effect of the event-triggered mechanism and two types of cyberattacks, the filtering error system model has been constructed. Two independent random variables obeying the Bernoulli distribution are introduced to describe the two types of cyberattacks. Sufficient conditions that can guarantee the admissibility of the filtering error system have been developed with Lyapunov stability theory and LMIs techniques. Moreover, the co-design method is present in terms of LMIs to derive the parameters of dynamic event-triggered mechanism and the designed [Formula: see text] filter synchronously. Finally, an illustrative example is employed to verify the usefulness of the proposed method.

Stability Analysis and Controller Design of Networked Active Vehicle Suspension System Subject to Delays and Packet Losses

In this paper, the stability analysis and control design of networked control systems (NCS) subject to network induced delay and packet dropouts, the study is aiming to maximize the allowable upper bound of network induced delay together with the number of consecutive packet dropouts, The analysis method utilizes a new Lyapunov-Krasovskii (LKF) functional to provide less conservative results. The delay-dependent stability criteria based on improved Wirtinger inequality and reciprocally convex combination inequality are derived in terms of linear matrix inequalities (LMI). Finally, numerical examples are given to show the effectiveness of the proposed analysis method compared to other existing methods.

Output‐based event‐triggered control of networked systems subject to bilateral packet dropouts

In this paper, an output‐based event‐triggered control problem of discrete‐time networked control systems (NCSs) subject to bilateral packet dropouts is investigated. In view of stochastic sequences of packet dropouts in the measurement channels (from sensors to controller) and the control channels (from controller to actuators), the NCS is converted into a closed‐loop stochastic parameter system. In the aid of a Lyapunov functional based on stochastic variables, the sufficient conditions on design of a dynamic output feedback control law and bilateral event‐triggering conditions are derived to guarantee the exponentially mean‐square stability for NCSs. Furthermore, an improved iterative algorithm is given to obtain the output‐based control law and event‐triggering parameters from a set of nonconvex inequalities. Finally, a numerical example and the corresponding simulation results are given to illustrate the validity and applicability of the developed techniques.

Fuzzy Weighted Memory Event-Triggered Control for Networked Control Systems Subject to Deception Attacks

This paper considers the event-triggered control problem for a class of Networked Control Systems (NCS) subject to transmission delays and stochastic deception attacks. A new fuzzy weighted memory event-triggered mechanism is proposed to reduce the network bandwidth consumption and data transmission rates. In this context, a new fuzzy weighted memory state feedback controller is proposed to stabilize the closed-loop NCS. Considering the security problem of NCS, a randomly occurring deception attack model is employed, assuming bounded malicious signals injected by the attacker. Based on a suitable Lyapunov-Krasovskii functional, a design methodology is proposed, in terms of linear matrix inequalities, to synthesize both trigger parameters and NCS controller gains. Finally, a numerical example is considered to illustrated the effectiveness of proposed results, compared to previous ones from the literature.